Hardware-in-the-Loop for embedded system developers

Compact and fast for earlier testing

miniHIL fits on your work bench and allows embedded software developers to test their application after each and every code change.

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Matthias Spranz, Development Manager Hitex GmbH

Why test with miniHIL?

Everyone knows that software should be tested earlier and more often. Unfortunately, the reality is often different. Hardware that is controlled by embedded software frequently needs a HIL (Hardware-in-the-Loop) to test the product extensively. But a HIL is expensive, is typically used by several developers, and may even be shared across departments.

In order that every developer can profit daily from the advantages of a HIL system, PROTOS has developed the miniHIL. Around the size of a sheet of A4 paper, the miniHIL can be used daily, even hourly, to check the functionality of code changes. Thanks to the use of a model of the end application, bug fixes, code changes, and new concepts can be tried out without putting expensive hardware, e.g. motor drivers or inverters, at risk.

The miniHIL is also suitable for safety-critical applications. Using the test case language CaGe, extensive tests can be created that check applications as wide ranging as blood glucose meters or window lifters for possible errors.

How does the miniHIL work?

Click the image to learn more about miniHIL

The PROTOS miniHIL is a compact complete solution consisting of the miniHIL hardware board and a software platform for environment simulations and test cases.

  • With the miniHIL hardware, the pins of the target microcontroller are connected to the test system on the signal level.
  • The miniHIL software is used to develop and generate test cases and environment simulations with models. The environment simulations (e.g. for motors, batteries or bus protocols) are needed to make the System under Test (SUT) work completely without system hardware. This allows the SUT to be put into very many different situations very quickly and with little effort. This makes the test fully automatable for good and bad cases.

miniHIL Hardware Setup

Setting up your test system only requires a few simple steps:

  • Plug in your evaluation board as a system-under-test. This ensures your embedded application is tested on your target microcontroller.
  • Connect the hardware interfaces of the system-under-test to the test system.
  • Are you missing an interface or function? Just add the FPGA Board to the platform.
  • Develop environment simulations and test cases that run on the powerful, integrated embedded processor (STM32H7).
miniHIL Testaufbau

miniHIL test development

The tests and environment simulations for the miniHIL are developed in a model-driven manner. The basis for modeling is the open source tool eTrice that enables structure and behavior modeling and code generation. CaGe test models can be seamlessly integrated into eTrice models. This combination allows simple development of models that include both environment simulation and testing. Requirements for the development environment: Windows PC with 8 GB RAM and USB 2.0 ports.

A miniHIL model consists of the following parts:

  • Adapter library for controlling the hardware interfaces (eTrice models)
  • Simulation and monitoring elements based on the hardware interfaces (eTrice models)
  • Your test cases can directly access the hardware interfaces as well as the simulation and monitoring elements, e.g. for fault injection (CaGe models).

Areas of application for the miniHIL

What do you want to test?

The miniHIL is suitable for testing a wide range of products in which complex controls or safety-critical functions are implemented:

Examples of target microcontrollers (system under test):

  • ST-Microelectronics: STM32, STM8
  • Infineon: TLE, AURIX, XMC
  • NXP: S12
  • Microchip: dsPIC33
  • ARM Cortex-M
  • And, if your chosen processor isn’t listed, just let us know.

Many adapters for conventional MCU development boards are already available, while new ones for other processors can be developed on request.

Specifications for the miniHIL

Technical specifications


  • Power Supply – 24 V DC power supply; 5 V and 3.3 V on board.
  • Device Under Test (DUT) – Compatible with STM32 Nucleo and Arduino format boards. Adapters on request.
  • Test System Processor – STM32H743 MCU.
  • Interfaces and I/O – 18 analog outputs; 8 analog switches, 16 digital GPIOs; 2 controllable power supplies (brown-out testing).
  • Debugger – Integrated ST-Link for test system processor.
  • DUT Input/Output – 5 rotary potentiometers; 13 LEDs; 6 pressure switches; 6 DIP switches; CAN interface; 4 USB-to-UART interfaces.
  • Additional contents – Wire jumpers and USB cables.


  • eTrice – Eclipse-based development environment for the miniHIL.
  • CaGe – a programming language for modeling test cases.
  • SimModelLib – test and platform library.
  • SimRuntime – runtime environment for the tests.
  • Cube Project – example project, suitable for the integrated STM32H743 MCU.

Use cases for the miniHIL

The miniHIL is excellent for testing from the point where integration testing is needed. Examples can be found here:

Test for all typical microcontroller applications.

  • Test for STM32 systems
  • Test for Infineon TLE systems
  • Other microcontrollers on request

Driver Test

  • Peripheral driver tests for microcontrollers
  • MCAL Test for AUTOSAR

Test and simulation for motor control software

Environment simulation

  • Sensor simulations e.g. temperature, acceleration
  • Battery and battery management simulations
  • Building block simulations e.g. flash, RAM, gate-driver
  • Interface simulation via SPI, I2C, UART, analog, digital, …

Rest bus simulation

  • Test for CAN Bus protocols
  • Test for LIN Bus protocols
  • Test for TCP/IP protocols
  • Test for UART protocols
  • Test for XCP protocols


  • Commissioning and development of microcontroller software (stimulation and monitoring)
  • Test of project specific protocols

miniHIL Features

Test levels

  • Component test for drivers and hardware-related software
  • Integration test for embedded applications
  • Simulated system test
  • Acceptance test

Test system modeling

Reporting and Traceability for HIL Tests

HIL Test Automation

All technical documentation is located online in the miniHIL UserGuide..

What is your use case for the miniHIL?

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